A Comparative Analysis of Growth Zones in Four 

 Calcified Structures of Pacific Blue Marlin, Makaira 



nigricans 



Kevin T. Hill, Gregor M. Cailliet, and Richard L. Radtke 



ABSTRACT: Sagittae, vertebrae, and ana! and 

 dorsal fin spines collected from Pacific blue marlin 

 in Kona. Hawaii were evaluated for legibility and 

 interpretability of growth patterns, ease of collec- 

 tion and processing, and the precision of the resul- 

 tant annulus counts for use in estimating age. 

 Sagittae, and anal and dorsal fin spine sections 

 contained growth zones assumed to be annual 

 events and there was a linear relationship between 

 age estimates of corresponding samples. Vertebrae 

 had numerous minute growth increments, but con- 

 tained no marks which could be interpreted as an- 

 nual. While nonparametric tests revealed no signifi- 

 cant difference between age estimates from differ- 

 ent hardparts of the same fish, dorsal and anal 

 spine counts had the best agreement. Anal and 

 dorsal fin spines were more practical in terms of 

 ease of collection, processing, legibility, and inter- 

 pretation; however, age estimates of spine samples 

 from larger fish required a statistical replacement 

 of inner growth zones that were destroyed by 

 matrix expansion. Although more difficult to col- 

 lect and interpret, sagittae provide more detailed 

 age information. Mean length-at-estimated age 

 data based on anal spine band counts are also pre- 

 sented. 



Increased knowledge of billfish age and growth 

 is essential for sensible management of these 

 fisheries. Although there is a paucity of such 

 information for most billfish species, the West- 

 ern Pacific Fisheries Management Council was 

 forced to draft a management plan for the Pacific 

 blue marlin, Makaira nigricans, with only 

 cursory data (WPFMC 1985). This lack of infor- 

 mation is due to the many difficulties involved 

 with studies of large pelagic fish species (Prince 

 and Pulos 1983), compounded by lack of routine 

 samphng progi-ams by research agencies in the 

 Pacific region. 



Kevin T. Hill, University of Hawaii, Department of Zoologj-. 



2538 The Mall, Honolulu", HI 96822. 



Gregor M. Cailliet, Moss Landing Marine Laboratories, 



P.O. Box 450, Moss Landing, CA 95039-0450. 



Richard L. Radtke. Univei-sity of Hawaii, Oceanic Biologj', 



Hawaii Institute of Geophysics. Honolulu, HI 96822. 



Various calcified structures have been utilized 

 for age estimation of the Istiophoridae. Dorsal 

 spine sections have provided age estimate data 

 for Atlantic sailfish, Istiophorus platypterus 

 (Jolley 1974, 1977; Hedgepeth and Jolley 1983), 

 Atlantic white marlin, Tetrapterus albidtts, and 

 Atlantic blue marlin, Makaira nigricans (Prince 

 et al. 1984). Sagittal otoliths have been described 

 as potentially useful structures for ageing most 

 billfish species (Radtke 1981, 1983; Radtke and 

 Dean 1981; Radtke et al. 1982; Prince et al. 1984; 

 Wilson 1984; Cyr 1987). Jolley (1974) described 

 numerous circuli in the vertebrae of sailfish; 

 however, both scales and vertebrae have now 

 been dismissed as structures for age estimation 

 in billfish (Prince et al. 1984). 



Age estimation of Pacific blue marlin is still 

 in the developmental stages, and most data 

 have focused on sagittae (Radtke 1981; Wilson 

 1984), with little effort on other skeletal 

 structures. The objective of the present study 

 was to e.xamine, interpret, and quantitatively 

 compare growth patterns in the sagitta, 

 vertebrae, and dorsal and anal fin spines of blue 

 marlin from Kona, HI. Each structure was 

 evaluated in terms of ease of collection and 

 processing, legibility of gi'owth patterns, and 

 the relative precision of the resulting age 

 estimates. 



MATERIALS AND METHODS 



Pacific blue marlin were sampled at the 

 Hawaiian International Billfishing Tournaments 

 in Augusts 1982 (?; = 48), 1983 (« = 113), and 

 1984 (n = 98), and at the Kona Gold Jackpot 

 toin-nament in May 1983 {n = 20), Kailua-Kona, 

 HI. Additional spine samples were obtained 

 from the Pacific Gamefish Research Foundation 

 (n = 32), the Hawaii Fishing Agency {n = 2), 

 and the National Marine Fisheries Service, 

 Southeast Fisheries Center (a specimen from 

 Kona which was shipped to Miami for ta.xi- 

 dermy). Meristic data collected for each fish 

 included lower jaw-fork length (LJFL to 0.1 cm), 



Manuscript accepted April 1989. 

 Fisher>- Bulletin, U.S. 87: 829-843. 



829 



